The example at Killeen in County Mayo belongs to a class of site known in Irish as fulacht fiadh, a term loosely meaning cooking pit of the wild. The typical form is a crescent or horseshoe-shaped mound of fire-cracked stone and charcoal-dark soil, built up over repeated use rather than deliberate construction. The working principle was straightforward: stones were heated in a fire, then dropped into a water-filled trough, usually timber-lined and sunk into the ground, bringing the water to a boil quickly and efficiently. The accumulated shattered stones, discarded after each use, formed the mound itself.

Most burnt mounds in Ireland date to the Bronze Age, broadly between 1800 and 800 BC, though some have produced dates ranging outside that window. They tend to cluster near streams or marshy ground, which provided the reliable water supply the process required. Their precise function has been debated for decades. Cooking is the most widely accepted explanation, and experimental archaeology has demonstrated that the method works well for boiling large joints of meat. Other proposals include brewing, textile processing, and use as hot-water baths or sweat houses. In practice, different sites may have served different purposes, and the same site may have been used for several over its lifetime. The Killeen example sits within a county that has produced a considerable number of these monuments, Mayo's boggy and water-threaded landscape being particularly conducive to their survival.